This section is intended to provide a background for material that is described below and/or recited in the claims. This background section may include concepts that could be pursued, but are not necessarily ones that have been previously conceived or pursued. Unless specifically indicated otherwise, this section is not prior art to the description and claims in this application and nothing in this section is admitted to be prior art.
In the Universal Mobile Telecommunications System (UMTS) Terrestrial Radio Access Network (UTRAN), a packet switched network temporary mobile station identifier (P-TMSI) signature (P-TMSI signature) is used to authenticate and to authorize the transfer of user equipment (UE) context information. As is generally understood in the art, packet data protocol (PDP) context information for a UE is a record of parameter values that provides information needed to establish a connection. Those parameters can include information about a type of PDP context being used, Quality of Service (QoS) information, etc. Authentication and authorization is performed when UE context information is transferred between network entities of a single system, or between network entities of different systems, when a serving General Packet Radio Service (GPRS) support node (SGSN) changes. Such a change can occur when the UE is being handed off because of movement to a different location. In this manner, the old SGSN (i.e., the SGSN from which the UE is being transferred) can verify that a context transfer request from a new SGSN (i.e., the SGSN to which the UE is transferring, also called a transferee SGSN) is valid and relates to the UE identified in the context transfer request. Hop-by-hop signaling between network elements may be protected by network domain security (NDS) so that no outsider can modify packets.
The mechanisms for authentication of requests to transfer context information in an Evolved 3rd Generation Partnership Project (3GPP) system are different from those in legacy UMTS and GPRS systems. In an evolved 3GPP system (also known as Evolved UTRAN (E-UTRAN) or Long Term Evolution (LTE)), which is discussed for example in 3GPP Technical Specification (TS) 23.401, the P-TMSI signature is not expected to be used. Instead, the non-access stratum (NAS)-level security association and corresponding keys and COUNT values are managed during the IDLE mode. All NAS-level signaling is authenticated, by integrity protection, with the NAS keys. As described in TS 23.401 and as known in the art, UE mobility in an evolved 3GPP network is controlled by an element known as a Mobility Management Entity (MME). Functions of an MME can include NAS signaling, Mobility Management (MM), NAS signaling security, and authentication. During mobility from an old MME to a new MME, the old MME authenticates a context transfer request and mobility signaling based on an NAS-Token calculated with an integrity protection key.
When a UE moves between UMTS, Global System for Mobile Communications (GSM) or GPRS and an evolved 3GPP system, the context transfer and mobility signaling must still be authenticated. However, there is an issue with regard to how an evolved 3GPP system authorizes context transfer requests or mobility signaling that comes from a UMTS/GPRS system that does not provide the same authorization mechanisms as the evolved 3GPP system. In particular, a transferee UMTS/GPRS network node (a node into the domain of which a UE is transferring) expects a P-TMSI signature from a UE (i.e., a mobile terminal or other device). The UMTS/GPRS node then provides that P-TMSI signature to a peer network entity (e.g., an SGSN from which the UE is transferring) when requesting context information for that UE. However, the evolved 3GPP system (EPS) does not provide for P-TMSI signature handling. Indeed, parts of the information element (IE) that hold the P-TMSI signature in a UTRAN system signaling message may be used for a different purpose in an evolved 3GPP system. For example, some of the bits of that IE may be needed in an evolved 3GPP system to hold parts of the Evolved Packet System TMSI (S-TMSI). This reduces the available bits for using authentication material for context transfer authorization.